I underlined the Contact: information to point out that behind a NAT, the private IP address (192.168.0.2) should not appear in the Contact: information. Instead, the public IP address (172.181.0.254) should appear. If it does not, then the SIP Proxy cannot properly send you any SIP INVITEs for incoming calls.

I underlined the Contact: information to point out that behind a NAT, the private IP address (192.168.0.2) should not appear in the Contact: information. Instead, the public IP address (172.181.0.254) should appear. If it does not, then the SIP Proxy cannot properly send you any SIP INVITEs for incoming calls.